After two months of intense storms, the state of California shows “no extreme drought,” according to NOAA’s U.S. Drought Monitor. This news comes on the heels of a five-year drought in the state.

Meanwhile, ski resorts are piled high in snow, after more than 500 inches fell in the Sierra Nevada. The heavy rains flooded towns and threatened dams. The snowpack, which in the spring will melt to supply reservoirs during the summer, is at an estimated 180 percent of the average.

So can the state — and its farmers — breathe easy this year?

Ira discusses the weather, the climate, and what both mean for water with climatologist William Patzert and snow hydrologist Thomas Painter, both of NASA’s Jet Propulsion Laboratory. Then, he checks in with KQED water reporter Lauren Sommer, who’s been following the debate about how California’s water policy should respond to what may be the new normal of climate in the West.

Segment Guests

Bill Patzert

Bill Patzert is a Climatologist at NASA’s Jet Propulsion Laboratory in Pasadena, California.

Segment Transcript

IRA FLATOW: This is “Science Friday.” I’m Ira Flatow. After five years of parched lawns, dry farm fields, the drought is over in California, thanks to just two months of heavy rains.

The state has received more rain than the reservoirs can actually hold. Rivers are high. The snowpack is so deep that ski resorts are piled up to the tops of the chairlifts at some spots with the snow.

It’s not all frolicking in the water, though. Last month for example, nearly 200,000 people were evacuated from below the Orrville Dam. You’ve seen that pictures of that spillage there. It was very greatly damaged.

And across the state there are still torrential rains. They have fouled power lines, flooded roads, triggered mudslides. And is it right to say that the drought is over?

I mean what about recharging the aquifer? We need to do that. What can farmers count on for the dry summer months ahead?

Governor Jerry Brown says he’s waiting until April to make the call. But here to shine a light on where all that rain came from and where it may go, two researchers from NASA’s Jet Propulsion Laboratory in Pasadena, California. Bill Patzert, climatologist, and Tom Painter, snow hydrologist and principal investigator for the Airborne Snow Observatory. Welcome to “Science Friday.”

TOM PAINTER: Thanks for having us

IRA FLATOW: Bill?

BILL PATZERT: Happy Friday.

IRA FLATOW: Hey, happy Friday. Bill, what’s it been like to live in Southern California this last couple of months after so long a drought?

BILL PATZERT: Well, after about 17 years of on and off drought, Ira, everybody’s pretty giddy with all this snow pack and rainfall. But there are a couple of asterisks, as you mentioned. All the flooding has really caused over $600 million in damage to roads, bridges, and dams. But the bottom line, as sweet as this wet winter is, this is just a temporary fix. This is definitely no drought buster.

IRA FLATOW: No drought buster. What would you know? What would tell you that the drought is over? What do you need to see?

BILL PATZERT: Well, you have to go back. California, roughly a third of our water supply is snowpack. A third is imported water from the Colorado. And about a third is ground water. And ground water, which has been depleted severely over the past few years, will take years to replenish.

And of course, Lake Mead is precariously depleted. So simply, all this snow and rain is sweet. But we’re still facing an ongoing water crisis here in the West.

IRA FLATOW: So don’t get too happy too soon is your message. Tom, I remember when you’ve been on this show before. And you’ve gone out and surveyed the snowpack.

TOM PAINTER: That’s right.

IRA FLATOW: What did you see this year as compared to years past?

TOM PAINTER: Well, so we have seen an amazing amount of snow. We started our program in 2013. Some claim that we initiated the drought by starting to measure the snowpack with lasers. And the most amount of snow that we’ve measured was just a month ago when we started flying again this year over the Sierra Nevada.

There are many places where the snowpack is over 50 feet deep and that was a month ago. It’s snowed considerably since then. So the flights that we’re doing today and over the next few days, we are pretty confident those are going to show areas with snow depths greater than 60 feet. I mean it really is a profound snowfall accumulation and a transformational landscape, especially for what we’ve seen over the last few years.

In terms of what Bill just mentioned, so the water usage, about 30% of that comes every year. 30% to 40% comes from snow melt runoff. But what he didn’t mention is that, of the precipitation that falls onto the landscape of California and really across the Western US, about 75% to 80% of that comes from snowfall. All right, so what gives with the difference?

Well, the difference is what he mentioned. It’s the pumping of ground water and the import of water from other domains. But over the long haul, the replenishment of those ground water supplies comes from what precipitation falls out of the sky. So over the long haul, you can’t have that difference in ratios and have it be fully sustainable.

So this is a fantastic year. And in terms of surface water, it’s a great thing. The reservoirs are filling up. The groundwater in the surface layers is filling up. And so we should get really good runoff this year.

IRA FLATOW: Mm-hmm. And so that would recharge the aquifers you’re hoping?

TOM PAINTER: That’s right. But it’s a long process. And so it doesn’t happen overnight. The overnight happens with respect to snowfall and rainfall at the surface. But getting into the deeper layers takes a long time.

In the month of January with the big atmospheric river events that we had here, the whole of the Sierra Nevada, our best understanding of how much water fell out of the sky is about 25% more than the annual flow of the Colorado River. And that was just in two sizable atmospheric river events.

IRA FLATOW: Well, let me ask both of you, what climate conditions will you have your eye on as the year unfolds to give you a better idea of what to expect waterwise?

BILL PATZERT: Well, let me take this one, Ira. California climate is one of the most variable of any state. Historically it swings from drought to flood to drought, but mostly drought.

Not only that, the West is warming. And as it warms, more and more precipitation will fall as rain and not as snow, which will create tremendous problems in water storage. But in spite of all this, California is the sixth largest economy in the world. It has a population of 40 million, a $60 billion dollar agricultural industry.

And so California has a tremendous thirst, but a dry climate. So looking ahead, the key here will be water conservation by everyone– farmers, city dwellers, and industry. And so it’s a warmer future, and it’s a water conservation future.

IRA FLATOW: There you have it. Let’s go to the phones to Ron in Ventura County. Hi, Ron. Welcome to “Science Friday.”

RON: Thank you. Yeah, I was calling because I just wanted to mention that western Ventura County is still in severe drought. I work with the Casitas Water District. And we’re in Stage Three. Our reservoir’s only at 43%. After five years of drought, one average rain isn’t going to kind of get us out of it yet.

IRA FLATOW: That’s interesting. So you’re still under water restrictions?

RON: Yes, absolutely.

IRA FLATOW: And so this rain, all this rain we hear about didn’t help you very much?

RON: A lot of the rain went north and went south. So Lake Cachuma, which is in Santa Barbara County and Lake Piru, which is off on western Ventura County, have not fully recovered as a result of the rains. Well, we were, like I said, limited in what we received compared to the rest of the state.

IRA FLATOW: All right. Thanks for that update. Tom, how does rain in the mountains, you’ve been up there. How did that affect the snowpack that you’ve seen?

TOM PAINTER: Well, in response to that and the caller’s comment, I just wanted to point out that in the northern Sierra Nevada, we’re at about 80% of the value for this date for 1982-83, which is on record for being the largest year on record across that region and across California. In the central Sierra Nevada, we’re just a little bit below that peak of 1982-83. And in the southern Sierra, we’re right on track with that year. So as he mentioned, there is this spatial variability in the accumulation of the precipitation. And not only across the Sierra Nevada, but also in the lower lands of California.

Now in terms of rain, so those are the snowpack measurements that I just described. But in 1982-83, it was a distinctly colder year. And so there was not very much rain that happened during the year.

In this year, some of the early storms in the fall and then into December, January, had considerable amounts of rainfall as well. So the accumulation of precipitation, even though the snowpack reflects a certain number that is catching up with 1982-83, arguably there’s been more precipitation than there was in that year, at least across the Sierra Nevada. Now what happens with the rainfall in the mountains?

As Bill was alluding to, as the rain snow line increases in elevation, then more of that landscape is getting rain falling on it. And what happens with rain? It flows downhill. What happens with snow? It stays intact.

And in staying intact there, it is a reservoir. So in the Western US, what allows the civilization to exist with the kind of numbers that we have is that we have this dual reservoir system– well, actually three reservoir systems. One is the mountain snowpack, which has always been there. The other is the groundwater, which has always been there.

And then the human built reservoir systems that we rely on as well to modulate between those two. And so as more of that precipitation falls as rain, it runs off quickly and displaces reservoir capacity in the human built reservoir. So that works towards shrinking water supply. And as we saw this year, many of the reservoirs had to go into heavy releases of water to avert disaster, destruction of dams, massive flooding, et cetera.

IRA FLATOW: All right. Well, thank you both for taking time to be with us today. Bill Patzert is a climatologist, And Tom Painter, a snow hydrologist, principal investigator, for the Airborne Snow Observatory, both out of NASA’s JPL in Pasadena. Good luck to you. And thanks for taking time to be with us today.

TOM PAINTER: Thanks, Ira.

IRA FLATOW: You’re welcome.

BILL PATZERT: My pleasure.

IRA FLATOW: Thank you. We want to now turn to the so what question of all of this. And that would be policy, water policy. What should we actually do with the data on how precipitation may be changing in the West? Do we need to replace those aging dams? Do we need to build more?

KQED San Francisco water reporter Lauren Sommer joins me now. She’s been following the conversations about how the state of California should manage its water. Welcome back, Lauren.

LAUREN SOMMER: Hi, Ira.

IRA FLATOW: Our last guests were in the LA area. What’s the mood in the Bay Area been about all of this rain?

LAUREN SOMMER: Yeah, I think shock is a fair word. I mean we spent five years hearing about we need to conserve, we need to cut back, about how dry it is. And there’s just, as you’ve heard, this torrential amount of precipitation and snow and rain. And I think people are still reeling here.

IRA FLATOW: This is “Science Friday” from PRI, Public Radio International. So you have a piece for KQED, arguing essentially that the water system in California as it exists cannot handle California’s changing precipitation patterns. Why not?

LAUREN SOMMER: Yeah, I mean we heard a little bit about this just now. That it’s designed around the snowpack in the Sierra Nevada. It’s like this big frozen reservoir. It keeps the snow and precipitation up there through the winter, and then it slowly melts kind of in the late spring, down the rivers, and feeds California throughout the summer, which is the dry period, when we need it.

If, as we’ve heard, more of that precipitation is going to fall as rain instead of snow, well that frozen reservoir is shrinking. And we have to catch more of that during the winter months. And that’s where we’re running into some problems right now.

There’s just so much water in the system that we’re seeing reservoirs really hit their capacity. And downstream of the reservoirs, there are things like river channels and levees and flood infrastructure that’s also been inundated. And we’ve seen a number of levees breach recently.

IRA FLATOW: Yeah, well, we saw that famous Orrville Dam spillway. That was a disaster, from the way that water was rushing over. And I’ve heard Californians tell me, when I bring up the subject of running out of water, they say, well, we don’t have enough reservoirs. We need to build more reservoirs. And if we’re having liquid water, now instead of the snow, wouldn’t that be an argument for that?

LAUREN SOMMER: Yeah, it sounds like a simple question, right? But of course, it’s not a simple answer. One basic thing that’s happened over time– we’ve used all the really good places for dams in this state. There’s just not a lot of places on these rivers where we can build big dam projects anymore.

And the other thing that people really like to point out is that we talked a little bit about the groundwater. That’s a vast storage area for water in this state. Some people say it’s 10 times larger than all of our reservoir capacity. And so you’re seeing experiments, actually, right now, where people are taking some of these flood waters they’re kind of spreading it out over farmland and cropland and letting it percolate back into the aquifers. Because that’s kind of a way to recharge some of these aquifers and keep the water stored there so we don’t have to keep it in the reservoirs.

IRA FLATOW: Why has this winter thrown such a spotlight on water policy? Is it just the flooding that’s happening?

LAUREN SOMMER: I mean we kind of traded one crisis for another, right? And everyone likes a good crisis.

IRA FLATOW: Because we know about the drought, now you’re hitting with just the opposite, right?

LAUREN SOMMER: Yeah, and it’s important to remember floods and droughts are not new for California. But some people are saying that this should be a wake up call. Because climate change is expected to make the extremes more extreme in California. So droughts are still going to happen naturally, but if it’s hotter, the droughts might be a little bit worse. And in the winters, if the winters are a little warmer, we get less snow and more rain. So this is a natural cycle for California. But because we’ve seen these two events so close together, some people are saying, well, hey, California, we might need to really think about designing our water system for a future where we’re going to see more of this extreme.

IRA FLATOW: Well, can you read any of the political tea leaves about which way that might go? I mean, where the money will come from?

LAUREN SOMMER: That’s always the challenge. And there is a very large backlog already in terms of things like levee maintenance and flood control infrastructure. So there’s already some catch up work to do here in the state.

The voters of California passed a very large water bond back in 2014. And so some of that money still needs to be spent. And there’s a big debate going on right now about whether that should go to large dam projects or things like ground water recharge, or just kind of shoring up the flood infrastructure throughout the state. So there definitely is a source of money there. It’s not going to cover everything. And people are also waiting to hear what President Trump might do with his infrastructure spending. He’s promised a lot of development in that area.

IRA FLATOW: Well, as they say, so goes California, so goes the rest of the country. So we will be watching all of us around here to see how that works out. Thank you, Lauren. Thanks for your work.

LAUREN SOMMER: Thanks.

IRA FLATOW: Lauren Sommer, water environment and energy reporter for KQED in San Francisco. One last thing before we go. It’s March, and you know what that means. Time for Mars Madness. That’s right, I said Mars, as in the planet.

You can find lots of red hot stories, get it? Like why Mars is BYOB, bring your own bacteria. If we go to Mars and settle it, you might want to bring our own bacteria. Great story up on our website at sciencefriday.com/MarsMadness. No bouncing balls involved.

PJ Lederman composed our theme music. Our thanks to our production partners at the studios of the City University of New York. If you’d like to write us, please send your letters to “Science Friday,” 19 West 44th Street, Room 412, New York, New York 10036.

And you can email us SciFri@sciencefriday.com. And you know where to find us online in social communities, up there on our website and on Facebook and Twitter. “Science Friday” is available all week long. Have a great weekend! I’m Ira Flatow in New York.

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